As used herein, the term "precolored" means that a colorant, such as a pigment or dye, is added to a polymer prior to melt extrusion to form fibers. The term "yarn" means a continuous strand of fiber or fibers in a form suitable for knitting, weaving or other interweaving into a textile fiber. The term "piece dye" means dyeing of fabrics in fabric form after weaving or knitting as opposed to dyeing in the yarn.
Fabrics which can be supplied uncolored and which have a pattern after dyeing have advantages over fabrics which are made from package dyed yarns. For example, uncolored fabrics which demonstrate a pattern after piece dyeing are very versatile. These fabrics can be supplied to the user, who selects the color to coordinate with other features of the end product. Where automotive uses are intended, the uncolored fabric may be dyed blue to match a blue interior or red to match a red interior. Whether red or blue, the fabric will have a predetermined pattern. The fabric maker no longer must keep a large selection of yarn dyed materials to fill orders for patterned fabric.
Polyester yarns are known to be readily dyed using disperse dyes in aqueous systems. Typically, fabrics from these polyester yarns are dyed under pressure and at temperatures of 130.degree. C. to 150.degree. C. and then heatset. This method of dyeing polyester fabrics is popular because the polyester fabric readily takes the disperse dyes under the pressure and temperature conditions, producing good, consistent color. However, the method does not readily allow patterns, for example, pin stripes within the fabric, since all of the polyester fiber will take the dye during the dyeing operation.
Polyolefins, on the other hand, are known in the art as difficult if not impossible to dye using disperse dyes in water or water-carrier systems. In general, polyolefins are extremely hydrophobic so that the water and other dye carriers in the dye bath do not penetrate the polyolefin fiber to an extent great enough to produce a good dye color. Modified polyolefins are known. U.S. Pat. No. 2,957,225 to Welch et al. describes a fiber of poly(4-methyl-1-pentene), which is produced under special conditions and polymerized with a special type of catalyst composition composed of particular metal halide salts having certain alkyl groups attached thereto.
It is known that poly(4-methyl-1-pentene) is difficult to dye without modification of the polymer. U.S. Pat. No. 3,102,869 to Coover, Jr., et al. discloses a dyeable poly-alpha-olefin, including polymethylpentene, fiber containing polyvinyl acetal resins to provide dyeability of the normally non-dyeable polyolefin fiber. U.S. Pat. No. 3,375,213 to Press describes a method of modifying polyolefins with synergistic polymeric combinations to allow dyeability under conditions normally used for polyester fabrics.
Due to the relatively high temperatures involved in dyeing and heatsetting of polyester, most polyolefin materials would not survive this processing intact. That is, many polyolefin fibers subjected to these high temperatures would soften, resulting in a loss of molecular orientation and a corresponding loss in strength of the fiber. Softening can also result in a loss of texture or crimp in the fiber, which in turn gives an appearance of less fiber for a given weight of fiber (less bulk). In some cases, polyolefin filaments soften or even melt to the point that filaments within the yarn bundle and even between yarn bundles adhere to one another. This causes a loss of strength and appearance in the fabric. An additional effect on some of the more commonly used polyolefins is that, due to the lower melting points and glass transition temperatures, dyes in the dyebath could more easily penetrate into these fibers. But polymethyl pentene absorbs considerably less dyestuff.
Surprisingly, it has been discovered that certain polymethylolefin fibers can be combined with polyester fibers to make a fabric which can be piece dyed using disperse dyes and dyeing systems to produce a multi-color patterned primarily polyester fabric without detriment to the polymethylolefin. Such a fabric is especially desirable for automotive uses. For automotive uses, upholstery is most often polyester and prevalent dyeing techniques produce solid color fabrics. It is believed that present patterned automotive fabrics are created with package dyed yarns. At least two different colored yarns are made into a fabric having the preselected pattern. A multi-colored fabric produced by dyeing rather than specially weaving two preselected color threads represents a substantial advance in economy and versatility.